Sugar cane growing uses mechanization techniques extensively and these techniques have resulted in sugar cane harvesters being used which are satisfactory for the crop conditions under which they are used. Present harvesters, however, with few exceptions, are adapted to cut burned cane. This is crop which has had the trash cover burned prior to cutting and which, therefore, reduces by a large portion the percentage of chaff or trash to cane which enters the harvester.
As opposed to this practice, "green cane cutting" has become a favoured method in some circumstances. Green cane cutting is desirable since burning requires additional labour and is dangerous. Further, green cane cutting allows harvesting flexibility during wet weather.
Nevertheless, the art of mechanically cutting green cane is in its infancy and the problems associated with its cutting have not been fully investigated. Bearing this in mind, it should be understood that the explanations herein are believed to be correct but that they may nevertheless prove to be incorrect or qualified in the years to come as further knowledge of green cane harvesting becomes available.
In harvesters used for cane harvesting, the cleaning assembly is the area of primary concern. Uniform air distribution throughout the cleaning system is desirable since this will more efficiently separate the cane from the chaff or crop trash such as loose leaves and the like. When unburned crop is being harvested, the cleaning system is under additional labor to adequately separate the crop from the chaff for milling purposes. While various cleaning systems have been used for green cane harvesting, there are disadvantages inherent in all.
For example, some burned cane harvesters have been used for green cane cutting. These harvesters, while satisfactory at low speeds due to the ability of the cleaning system of the harvester to accept relatively low speed loading, are not able to harvest crop at the large capacities which are desirable due to the configuration of the machine, the inefficiency of the cleaning system and the general ability of the machine to accept heavy loading.
Harvesters used for green cane harvesting may suffer various other disadvantages. For example, a harvester may be adapted for one-row cutting only. One-row cutting is not desirable because the harvester must travel between rows which is inefficient. This particular disadvantage is caused by the configuration of the cleaning and conveying system which is required, in part, by the cleaning requirements of green cane harvesting.
A further problem relates to present drive systems which are used for driving the chopper rollers in harvesters. Chopper rolls may jam if the soil is rocky or debris laden. At the same time, the chopper rolls have relatively little inertia by themselves and, therefore, without some additional inertia compensation, they cannot adequately cut the billets when the crop mat suddenly increases. To overcome this problem, a flywheel is ordinarily connected to the chopper rolls. In one design, the flywheel, through reduction gears, drives the chopper rolls, the flywheel being driven by the source of harvester power. In the event the chopper rolls jam however, the large inertia of the flywheel is transmitted to the chopper rolls and since the reduction gears further amplify the inertia force of the flywheel, damage to the chopper rolls can result. To prevent this damage, unnecessarily elaborate release mechanisms have been designed.
Similarly, it is also desirable to provide a reversal to the chopper rolls in the event of jamming so as to attempt to free the rolls. Methods used to accomplish this with flywheel driven chopper rolls, however, have been unsatisfactory, again because they are over-elaborate and do not provide full operating power in the reverse direction.
Yet a further problem relates to a desire to achieve uniform crop distribution in the cleaning area of a sugar cane harvester. Uniform crop distribution is difficult to achieve because of the various varieties of sugar cane and the crop conditions under which cane is harvested. Further, the speed of the chopper rolls may usually be changed to increase or decrease the billet length of the cane which also affects crop distribution in the cleaning area.
Yet still a further problem relates to the conveyancing of the cut crop from the base cutter to the chopper rolls. The crop mat which is being conveyed should be substantially uniform across the width of the conveying passage. The feed rolls, used for conveying the crop, should provide a uniform conveying speed to the crop mat and a uniform pressure on the crop. Hydraulic flow dividers have been used for the feed rolls. These are inefficient and reduce power.